Chloro-(2’-chloro)trityl Polystyrene Resins

A very acid sensitive resin suitable for the synthesis of protected peptide fragments by the Fmoc strategy. In particular suitable for the preparation of C-terminal prolyl and cysteinyl peptides. Cleavage from this resin is achieved by using 1-95% TFA in CH₂Cl₂ (containing 8% triisopropylsilane), AcOH/CF₃OH/CH₂Cl₂, 0.5% TFA or hexafluoroisopropanol. Recently, this resin has been used in cyclization reactions under Heck reaction conditions, the solid phase synthesis of b-peptides via the Arndt-Eistert homologation of Fmoc-protected amino acid diazoketones and in Mannich reactions of alkynes, secondary amines and aldehydes in the presence of a copper (I) salt leading to the corresponding aminomethylalkynyl adducts.

This resin can also be used in Fmoc peptide synthesis. Carboxylic acids can be released under very mild acidic conditions by treatment with AcOH/TFE/DCM or HFIP in DCM. Completely protected peptides are generated under this conditions.

This resin is less sensitive towards acides compared to chlorotrityl resins.